Process for removing mercury from a coal tar product

ABSTRACT

A process for removing mercury from a coal tar product is described. A coal tar stream is contacted with a solvent to remove a product, and the product stream is contacted with an adsorbent material to remove elemental mercury, organic mercury compounds, and/or inorganic mercury compounds. Alternatively, the coal tar stream can be treated in a catalytic distillation zone of a fractionation zone.

This application claims the benefit of Provisional Application Ser. No.61/905,902 filed Nov. 19, 2013, entitled Process for Removing Mercuryfrom a Coal Tar Product.

BACKGROUND OF THE INVENTION

Many different types of chemicals are produced from the processing ofpetroleum. However, petroleum is becoming more expensive because ofincreased demand in recent decades.

Therefore, attempts have been made to provide alternative sources forthe starting materials for manufacturing chemicals. Attention is nowbeing focused on producing liquid hydrocarbons from solid carbonaceousmaterials, such as coal, which is available in large quantities incountries such as the United States and China.

Pyrolysis of coal produces coke and coal tar. The coke-making or“coking” process consists of heating the material in closed vessels inthe absence of oxygen to very high temperatures. Coke is a porous buthard residue that is mostly carbon and inorganic ash, which is used inmaking steel.

Coal tar is the volatile material that is driven off during heating, andit comprises a mixture of a number of hydrocarbon compounds. It can beseparated to yield a variety of organic compounds, such as benzene,toluene, xylene, naphthalene, anthracene, and phenanthrene. Theseorganic compounds can be used to make numerous products, for example,dyes, drugs, explosives, flavorings, perfumes, preservatives, syntheticresins, and paints and stains. The residual pitch left from theseparation is used for paving, roofing, waterproofing, and insulation.

The products from the coal tar often contain undesirable compounds, suchas mercury, which must be removed.

Thus, there is a need for improved processes for removing mercury fromcoal tar products.

SUMMARY OF THE INVENTION

One aspect of the invention is a process for removing mercury from acoal tar product. In one embodiment, the process includes providing acoal tar stream. The coal tar stream is contacted with a solvent in asolvent extraction zone to remove at least one product from the coal tarstream forming at least one product stream and a remainder coal tarstream, the at least one product stream containing one or more ofelemental mercury, organic mercury compounds, and inorganic mercurycompounds. The at least one product stream is contacted with anadsorbent material in an mercury removal zone, the adsorbent materialcomprising one or more adsorbents, an ion exchange resin, or mixturesthereof to remove the one or more of elemental mercury, organic mercurycompounds, and inorganic mercury compounds. The remainder coal tarstream is separated into at least two fractions.

In another embodiment, the process includes providing a coal tar stream,the coal tar stream containing one or more of elemental mercury, organicmercury compounds, and inorganic mercury compounds. The coal tar streamis introduced into a catalytic distillation zone of a fractionation zoneto separate the coal tar stream into at least two fractions, thecatalytic distillation zone positioned above the bottoms outlet andbelow the first product draw of the fractionation zone, the catalyticdistillation zone containing a catalyst, the organic and ionic mercurycompounds reacting in the presence of the catalyst to form elementalmercury in the reactive fractionation zone. At least one of thefractions is treated to remove the elemental mercury.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of one embodiment of the process of thepresent invention.

FIG. 2 is an illustration of another embodiment of the process of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows one embodiment of a mercury removal process 5 of thepresent invention. The coal feed 10 can be sent to the coking oven zone15, the gasification zone 20, or the coal feed 10 can be split into twoparts and sent to both.

In the coking oven zone 15, the coal is heated at high temperature,e.g., up to about 2,000° C. (3600° F.), in the absence of oxygen todrive off the volatile components. Coking produces a coke stream 25 anda coal tar stream 30. The coke stream 25 can be used in other processes,such as the manufacture of steel.

The coal tar stream 30 which comprises the volatile components from thecoking process can be sent to an optional contaminant removal zone 35,if desired.

The contaminant removal zone 35 for removing one or more contaminantsfrom the coal tar stream or another process stream may be located atvarious positions along the process depending on the impact of theparticular contaminant on the product or process and the reason for thecontaminant's removal, as described further below. For example, thecontaminant removal zone can be positioned upstream of the separationzone 45. Some contaminants have been identified to interfere with adownstream processing step or hydrocarbon conversion process, in whichcase the contaminant removal zone 35 may be positioned upstream of theseparation zone 45 or between the separation zone 45 and the particulardownstream processing step at issue. Still other contaminants have beenidentified that should be removed to meet particular productspecifications. Where it is desired to remove multiple contaminants fromthe hydrocarbon or process stream, various contaminant removal zones maybe positioned at different locations along the process. In still otherapproaches, a contaminant removal zone may overlap or be integrated withanother process within the system, in which case the contaminant may beremoved during another portion of the process, including, but notlimited to the separation zone or the downstream hydrocarbon conversionzone. This may be accomplished with or without modification to theseparticular zones, reactors or processes. While the contaminant removalzone is often positioned downstream of the hydrocarbon conversionreactor, it should be understood that the contaminant removal zone inaccordance herewith may be positioned upstream of the separation zone,between the separation zone and the hydrocarbon conversion zone, ordownstream of the hydrocarbon conversion zone or along other streamswithin the process stream, such as, for example, a carrier fluid stream,a fuel stream, an oxygen source stream, or any streams used in thesystems and the processes described herein. The contaminantconcentration is controlled by removing at least a portion of thecontaminant from the coal tar stream 30. As used herein, the termremoving may refer to actual removal, for example by adsorption,absorption, or membrane separation, or it may refer to conversion of thecontaminant to a more tolerable compound, or both.

The decontaminated coal tar stream 36 from the contaminant removal zone35 is sent to a solvent extraction zone 37.

In the solvent extraction process, a solvent stream 38 is introducedinto the solvent extraction zone 37 and contacts the decontaminated coaltar stream 36. At least one product 39 containing one or more ofelemental mercury, organic mercury compounds, and inorganic mercurycompounds is removed from the decontaminated coal tar stream 36.

The solvents used in the solvent extraction process can include, but arenot limited to, supercritical fluids, ionic liquids, polar solvents, andcombinations thereof.

Supercritical fluids are substances at a temperature and pressure abovethe critical point, where distinct liquid and gas phases do not exist.They have properties of both liquids and vapors. Suitable supercriticalfluids include, but are not limited to, supercritical carbon dioxide,supercritical ammonia, supercritical ethane, supercritical propane,supercritical butane, and supercritical water.

Ionic liquids are non-aqueous, organic salts composed of ions where thepositive ion is charge balanced with a negative ion. These materialshave low melting points, often below 100° C., undetectable vaporpressure, and good chemical and thermal stability. The cationic chargeof the salt is localized over hetero atoms, such as nitrogen,phosphorous, sulfur, arsenic, boron, antimony, and aluminum, and theanions may be any inorganic, organic, or organometallic species.Suitable ionic liquids include, but are not limited to,imidazolium-based ionic liquids, pyrrolidinium-based ionic liquids,pyridinium-based ionic liquids, sulphonium-based ionic liquids,phosphonium-based ionic liquids, ammonium-based and caprolactam-basedionic liquids, and combinations thereof.

Suitable polar solvents include, but are not limited to, pyridine,N-methyl pyrrolidone, methylene chloride, benzyl alcohol, formamide,dimethylformamide, dimethylsulfoxide, dimethylsuccinate,dimethyladipate, dimethylglutarate, propylene carbonate, methyl soyate,ethyl lactate, tripropylene glycol (mono)methyl ether 1,3-dioxolane, andcombinations thereof.

Alternatively, the extraction/adsorption zone described in U.S.application Ser. No. 61/905,898, entitled Process for Removing a Productfrom Coal Tar, filed Nov. 19, 2013 (Attorney Docket No. H0042311), whichis incorporated herein by reference, could be used in place of thesolvent extraction zone 37, if desired.

The products 39 from the solvent extraction process include, but are notlimited to, hydrocarbons that distill in the range of approximately 0°C. to 350° C. Depending upon the solvent used, the predominantfunctional groups may be heterocyclic aromatic, naphthenic orparaffinic, and may be ionic or neutral, acidic, or basic.

The product(s) 39 containing the elemental mercury, organic mercurycompounds, and inorganic mercury compounds is sent to a separation zone110 where a solvent stream 120 is separated from the product 115containing the elemental mercury, organic mercury compounds, andinorganic mercury compounds. The solvent stream 120 can be recycled tothe solvent extraction zone 37, if desired.

When organic mercury compounds are present, the product(s) 115 can besent to an optional conversion zone 125 where the organic mercurycompounds are converted to elemental mercury or inorganic mercurycompounds. Suitable conversion processes include, but are not limitedto, catalytic or thermal decomposition, catalytic reaction withhydrogen, reduction by transfer hydrogenation, precipitation withsulfide sources or elemental sulfur, and oxidation followed byreduction.

In one embodiment, the product(s) 115 containing the elemental mercury,organic mercury compounds, and inorganic mercury compounds is subjectedto hydroprocessing to convert the organic mercury compounds to inorganicor elemental mercury, followed by passage through a multi-layer bed forremoval of more than one type of contaminant. Other contaminants mayalso be converted to a form that is more easily removed by adsorption.

In another embodiment, the product(s) 115 containing the elementalmercury, organic mercury compounds, and inorganic mercury compounds issubjected to thermal processing at a temperature from about 100° C. toabout 900° C. in accordance with the teachings found in U.S. Pat. No.5,510,565 incorporated herein in its entirety. Organic mercury and otherimpurities are broken down to a form that is easier to remove byadsorption.

Alternatively, the separation zone 110 can be located after theconversion zone 125, if desired. However, the separation zone 110 isdesirably positioned before the conversion zone 125 because removing thesolvent first would result in less material being processed in theconversion zone 125.

The effluent 130 from the conversion zone 125 comprising the product(s)containing the elemental mercury, inorganic mercury compounds (whetheroriginal or converted organic mercury compounds (if present)), and anyunconverted organic mercury compounds is sent to a mercury removal zone135. The effluent 130 is contacted with an adsorbent material in themercury removal zone 135 to remove the elemental mercury and inorganicmercury compounds (whether original or converted organic mercurycompounds (if present)). A stream 140 of elemental mercury and inorganicmercury compounds is removed from the mercury removal zone 135 andfurther treated and/or recovered, if desired. The product(s) 145 with areduced mercury level is then recovered.

The elemental mercury and inorganic mercury compounds may be removed byadsorption, typically with transition metal sulfides, such as coppersulfide, or sulfur on activated carbon, activated aluminas, silica gelor molecular sieves. In addition, supported noble metals such as silver,palladium or platinum on molecular sieves or aluminas can be used.Certain zeolite/alumina hybrid adsorbents may also be used. The zeolitesthat can be used include, but are not limited to, faujasites (13X, CaX,NaY, CaY, ZnX), chabazites, clinoptilolites and LTA (3A, 4A, 5A)zeolites. Other adsorbents may be used including transition metals (suchas, copper, lead, antimony, manganese) oxides and carbonates inhydrocarbon streams that may contain sulfur compounds to convert themetals to a sulfide form that is active for mercury removal.

Another type of layer for mercury removal that is effective in thepractice of the present invention is sulfides of transition metals, suchas copper, silver, gold, lead, antimony and manganese.

Ion exchange materials may be used to remove mercury compounds. Ionexchange materials include, but are not limited to, ion exchange resinsand inorganic ion exchange materials. The ion exchange material can bean anionic exchange material or a cationic exchange material. Onesuitable adsorbent is an ion exchange resin that contains chemicallybound sulfide groups.

In some cases when the product(s) also contain H₂S or organic sulfurcompounds, the oxide or carbonate forms of the metals may be used tosulfide the metal in the adsorbent bed insitu and make it active formercury removal. This method of mercury scavenging may be usedeffectively for simultaneous removal of sulfur compounds and mercury.

In some case, the adsorbent is sulfur or a metal sulfide on an activatedcarbon support or an activated alumina support or other supports, suchas clays, to bind the active reagents for mercury removal in the form ofbeads or pellets.

In some embodiments, at least two products 39 are removed from thedecontaminated coal tar stream 36. The first product can be removedusing a first solvent, and then the second product can removed using asecond solvent, if desired.

The decontaminated coal tar feed 40 with at least one product removed issent to a separation zone 45 where it is separated into two or morefractions. Coal tar comprises a complex mixture of heterocyclic aromaticcompounds and their derivatives with a wide range of boiling points. Thenumber of fractions and the components in the various fractions can bevaried as is well known in the art. A typical separation processinvolves separating the coal tar into four to six streams. For example,there can be a fraction comprising NH₃, CO, and light hydrocarbons, alight oil fraction with boiling points between 0° C. and 180° C., amiddle oil fraction with boiling points between 180° C. to 230° C., aheavy oil fraction with boiling points between 230 to 270° C., ananthracene oil fraction with boiling points between 270° C. to 350° C.,and pitch.

The light oil fraction contains compounds such as benzenes, toluenes,xylenes, naphtha, coumarone-indene, dicyclopentadiene, pyridine, andpicolines. The middle oil fraction contains compounds such as phenols,cresols and cresylic acids, xylenols, naphthalene, high boiling taracids, and high boiling tar bases. The heavy oil fraction containsbenzene absorbing oil and creosotes. The anthacene oil fraction containsanthracene. Pitch is the residue of the coal tar distillation containingprimarily aromatic hydrocarbons and heterocyclic compounds.

As illustrated, the coal tar feed 40 is separated into gas fraction 50containing gases such as NH₃ and CO as well as light hydrocarbons, suchas ethane, hydrocarbon fractions 55, 60, and 65 having different boilingpoint ranges, and pitch fraction 70.

Suitable separation processes include, but are not limited tofractionation, crystallization, and inclusion compound formation.

One or more of the fractions 50, 55, 60, 65, 70 can be furtherprocessed, as desired. As illustrated, fraction 60 can be sent to one ormore hydrocarbon conversion zones 75, 80. For example, where hydrocarbonconversion zone 80 includes a catalyst which is sensitive to sulfur,fraction 60 can be sent to hydrocarbon conversion zone 75 forhydrotreating to remove sulfur and nitrogen. Effluent 85 is then sent tohydrocarbon conversion zone 80 for hydrocracking, for example, toproduce product 90.

Suitable hydrocarbon conversion zones include, but are not limited to,hydrotreating zones, hydrocracking zones, transalkylation zones,selective hydrogenation or complete hydrogenation zones, oxidationzones, and thermal conversion zones.

Hydrotreating is a process in which hydrogen gas is contacted with ahydrocarbon stream in the presence of suitable catalysts which areprimarily active for the removal of heteroatoms, such as sulfur,nitrogen, and metals from the hydrocarbon feedstock. In hydrotreating,hydrocarbons with double and triple bonds may be saturated. Aromaticsmay also be saturated. Typical hydrotreating reaction conditions includea temperature of about 290° C. (550° F.) to about 455° C. (850° F.), apressure of about 3.4 MPa (500 psig) to about 6.2 MPa (900 psig), aliquid hourly space velocity of about 0.5 hr⁻¹ to about 4 hr⁻¹, and ahydrogen rate of about 168 to about 1,011 Nm³/m³ oil (1,000-6,000scf/bbl). Typical hydrotreating catalysts include at least one Group 8metal, preferably iron, cobalt and nickel, and at least one Group 6metal, preferably molybdenum and tungsten, on a high surface areasupport material, preferably alumina. Other typical hydrotreatingcatalysts include zeolitic catalysts, as well as noble metal catalystswhere the noble metal is selected from palladium and platinum.

Hydrocracking is a process in which hydrocarbons crack in the presenceof hydrogen to lower molecular weight hydrocarbons. Typicalhydrocracking conditions may include a temperature of about 290° C.(550° F.) to about 468° C. (875° F.), a pressure of about 3.5 MPa (500psig) to about 20.7 MPa (3000 psig), a liquid hourly space velocity(LHSV) of about 1.0 to less than about 2.5 hr⁻¹, and a hydrogen rate ofabout 421 to about 2,527 Nm³/m³ oil (2,500-15,000 scf/bbl). Typicalhydrocracking catalysts include amorphous silica-alumina bases orlow-level zeolite bases combined with one or more Group VIII or GroupVIB metal hydrogenating components, or a crystalline zeolite crackingbase upon which is deposited a Group VIII metal hydrogenating component.Additional hydrogenating components may be selected from Group VIB forincorporation with the zeolite base.

Fluid catalytic cracking (FCC) is a catalytic hydrocarbon conversionprocess accomplished by contacting heavier hydrocarbons in a fluidizedreaction zone with a catalytic particulate material. The reaction incatalytic cracking is carried out in the absence of substantial addedhydrogen or the consumption of hydrogen. The process typically employs apowdered catalyst having the particles suspended in a rising flow offeed hydrocarbons to form a fluidized bed. In representative processes,cracking takes place in a riser, which is a vertical or upward slopedpipe. Typically, a pre-heated feed is sprayed into the base of the riservia feed nozzles where it contacts hot fluidized catalyst and isvaporized on contact with the catalyst, and the cracking occursconverting the high molecular weight oil into lighter componentsincluding liquefied petroleum gas (LPG), gasoline, and a distillate. Thecatalyst-feed mixture flows upward through the riser for a short period(a few seconds), and then the mixture is separated in cyclones. Thehydrocarbons are directed to a fractionator for separation into LPG,gasoline, diesel, kerosene, jet fuel, and other possible fractions.While going through the riser, the cracking catalyst is deactivatedbecause the process is accompanied by formation of coke which depositson the catalyst particles. Contaminated catalyst is separated from thecracked hydrocarbon vapors and is further treated with steam to removehydrocarbon remaining in the pores of the catalyst. The catalyst is thendirected into a regenerator where the coke is burned off the surface ofthe catalyst particles, thus restoring the catalyst's activity andproviding the necessary heat for the next reaction cycle. The process ofcracking is endothermic. The regenerated catalyst is then used in thenew cycle. Typical FCC conditions include a temperature of about 400° C.to about 800° C., a pressure of about 0 to about 688 kPa g (about 0 to100 psig), and contact times of about 0.1 seconds to about 1 hour. Theconditions are determined based on the hydrocarbon feedstock beingcracked, and the cracked products desired. Zeolite-based catalysts arecommonly used in FCC reactors, as are composite catalysts which containzeolites, silica-aluminas, alumina, and other binders.

Transalkylation is a chemical reaction resulting in transfer of an alkylgroup from one organic compound to another. Catalysts, particularlyzeolite catalysts, are often used to effect the reaction. If desired,the transalkylation catalyst may be metal stabilized using a noble metalor base metal, and may contain suitable binder or matrix material suchas inorganic oxides and other suitable materials. In a transalkylationprocess, a polyalkylaromatic hydrocarbon feed and an aromatichydrocarbon feed are provided to a transalkylation reaction zone. Thefeed is usually heated to reaction temperature and then passed through areaction zone, which may comprise one or more individual reactors.Passage of the combined feed through the reaction zone produces aneffluent stream comprising unconverted feed and product monoalkylatedhydrocarbons. This effluent is normally cooled and passed to a strippingcolumn in which substantially all C5 and lighter hydrocarbons present inthe effluent are concentrated into an overhead stream and removed fromthe process. An aromatics-rich stream is recovered as net stripperbottoms, which is referred to as the transalkylation effluent.

The transalkylation reaction can be effected in contact with a catalyticcomposite in any conventional or otherwise convenient manner and maycomprise a batch or continuous type of operation, with a continuousoperation being preferred. The transalkylation catalyst is usefullydisposed as a fixed bed in a reaction zone of a vertical tubularreactor, with the alkylaromatic feed stock charged through the bed in anupflow or downflow manner. The transalkylation zone normally operates atconditions including a temperature in the range of about 130° C. toabout 540° C. The transalkylation zone is typically operated atmoderately elevated pressures broadly ranging from about 100 kPa toabout 10 MPa absolute. The transalkylation reaction can be effected overa wide range of space velocities. That is, volume of charge per volumeof catalyst per hour; weight hourly space velocity (WHSV) generally isin the range of from about 0.1 to about 30 hr⁻¹. The catalyst istypically selected to have relatively high stability at a high activitylevel.

Hydrogenation involves the addition of hydrogen to hydrogenatablehydrocarbon compounds. Alternatively hydrogen can be provided in ahydrogen-containing compound with ready available hydrogen, such astetralin, alcohols, hydrogenated naphthalenes, and others via a transferhydrogenation process with or without a catalyst. The hydrogenatablehydrocarbon compounds are introduced into a hydrogenation zone andcontacted with a hydrogen-rich gaseous phase and a hydrogenationcatalyst in order to hydrogenate at least a portion of thehydrogenatable hydrocarbon compounds. Typical hydrogenation catalystinclude Group VIB (Cr, Mo, W), Group VIIB (Mn, Tc, Re) or Group VIIIB(Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) metals and combinations thereofsupported on an inorganic oxide, carbide or sulfide support, includingAl₂O₃, SiO₂, SiO₂—Al₂O₃, zeolites, non-zeolitic molecular sieves, ZrO₂,TiO₂, ZnO, and SiC. The catalytic hydrogenation zone may contain afixed, ebulated or fluidized catalyst bed. This reaction zone istypically at a pressure from about 689 k Pa gauge (100 psig) to about13790 k Pa gauge (2000 psig) with a maximum catalyst bed temperature inthe range of about 177° C. (350° F.) to about 454° C. (850° F.). Theliquid hourly space velocity is typically in the range from about 0.2hr⁻¹ to about 10 hr⁻¹ and hydrogen circulation rates from about 200standard cubic feet per barrel (SCFB) (35.6 m³ /m³) to about 10,000 SCFB(1778 m³ /m³).

Oxidation involves the oxidation of hydrocarbons to oxygen-containingcompounds, such as aldehydes. The hydrocarbons include alkanes, alkenes,typically with carbon numbers from 2 to 15, and alkyl aromatics, Linear,branched, and cyclic alkanes and alkenes can be used. Oxygenates thatare not fully oxidized to ketones or carboxylic acids can also besubjected to oxidation processes, as well as sulfur compounds thatcontain —S—H moieties, thiophene rings, and sulfone groups. The processis carried out by placing an oxidation catalyst in a reaction zone andcontacting the feed stream which contains the desired hydrocarbons withthe catalyst in the presence of oxygen. The type of reactor which can beused is any type well known in the art such as fixed-bed, moving-bed,multi-tube, CSTR, fluidized bed, etc. The feed stream can be flowed overthe catalyst bed either up-flow or down-flow in the liquid, vapor, ormixed phase. In the case of a fluidized-bed, the feed stream can beflowed co-current or counter-current. In a CSTR the feed stream can becontinuously added or added batch-wise. The feed stream contains thedesired oxidizable species along with oxygen. Oxygen can be introducedeither as pure oxygen or as air, or as liquid phase oxidants includinghydrogen peroxide, organic peroxides, or peroxy-acids. The molar ratioof oxygen (O₂) to substrate to be oxidized can range from about 5:1 toabout 1:10. In addition to oxygen and alkane or alkene, the feed streamcan also contain a diluent gas selected form nitrogen, neon, argon,helium, carbon dioxide, steam or mixtures thereof. As stated, the oxygencan be added as air which could also provide a diluent. The molar ratioof diluent gas to oxygen ranges from greater than zero to about 10:1.The catalyst and feed stream are reacted at oxidation conditions whichinclude a temperature of about 25° C. to about 600° C., a pressure ofabout 101 kPa to about 5,066 kPa and a space velocity of about 100 toabout 100,000 hr⁻¹.

Thermal conversion involves heating the composition to effect thechemical change. The thermal conversion can be any suitable process,such as a delayed coking or slurry hydrocracking zone. The hydrocarbonsare heated and fed into the bottom of one or more coking drums where thefirst stages of thermal decomposition reduce the hydrocarbons to a veryheavy tar or pitch which further decomposes into solid coke. Typically,the vapors formed during the decomposition produce pores and channels inthe coke through which the incoming oil from the furnace may pass. Thisprocess may continue usually until the drum is filled to a desired levelwith a mass of coke. The vapors formed in the process can exit the topof the coking drum and can be further processed. The resulting coke isremoved from the coking drum.

Slurry hydrocracking involves combining a catalyst with the hydrocarbonstream. The slurry stream typically has a solids content of about0.01-about 10%, by weight.

The slurry stream and the recycle gas can enter a heater. The recyclegas typically contains hydrogen, which can be once-through hydrogenoptionally with no significant amount of recycled gases. Alternatively,the recycle gas can contain recycled hydrogen gas optionally with addedhydrogen as the hydrogen is consumed during the one or morehydroprocessing reactions. The recycle gas may be essentially purehydrogen or may include additives such as hydrogen sulfide or lighthydrocarbons, e.g., methane and ethane. Reactive or non-reactive gasesmay be combined with the hydrogen introduced into the upflow tubularreactor or slurry hydrocracking reactor at the desired pressure toachieve the desired product yields. Often, slurry hydroprocessing iscarried out using reactor conditions sufficient to crack at least aportion of the hydrocarbon stream to lower boiling products, such as oneor more distillate hydrocarbons, naphtha, and/or C1-C4 products.Conditions in the slurry hydrocracking reactor can include a temperatureof about 340° C. to about 600° C., a hydrogen partial pressure of about3.5-about 30 MPa and a space velocity of about 0.1-about 30 volumes ofthe hydrocarbon stream per hour per reactor or reaction zone volume.

Generally, the catalyst for the slurry hydrocracking reactor provides acomposition that is hydrophobic and resists clumping. Typically, theslurry catalyst composition can include a catalytically effective amountof one or more compounds having iron. Particularly, the one or morecompounds can include at least one of an iron oxide, an iron sulfate,and an iron carbonate. Other forms of iron can include at least one ofan iron sulfide, a pyrrhotite, and a pyrite. What is more, the catalystcan contain materials other than an iron, such as at least one ofmolybdenum, nickel, and manganese, and/or a salt, an oxide, and/or amineral thereof. Preferably, the one or more compounds includes an ironsulfate, and more preferably, at least one of an iron sulfatemonohydrate and an iron sulfate heptahydrate. Alternatively, one or morecatalyst particles can include about 2-about 45%, by weight, iron oxideand about 20-about 90%, by weight, alumina. In some embodiments, thecatalyst is supported. The support can be alumina, silica, titania, oneor more aluminosilicates, magnesia, bauxite, coal and/or petroleum coke,for example. Such a supported catalyst can include a catalyticallyactive metal, such as at least one of iron, molybdenum, nickel, andvanadium, as well as sulfides of one or more of these metals. Generally,the catalyst can have about 0.01-about 30%, by weight, of the catalyticactive metal based on the total weight of the catalyst.

In some processes, all or a portion of the coal feed 10 is mixed withoxygen 95 and steam 100 and reacted under heat and pressure in thegasification zone 20 to form syngas 105, which is a mixture of carbonmonoxide and hydrogen. The syngas 105 can be further processed using theFischer-Tropsch reaction to produce gasoline or using the water-gasshift reaction to produce more hydrogen.

FIG. 2 shows an alternate mercury removal process 205. The coal feed 210is sent to the coking oven zone 215. A second portion can be sent to thegasification zone (not shown), if desired. Coking produces a coke stream225 and a coal tar stream 230.

The coal tar stream 230 which comprises the volatile components from thecoking process is sent to fractionation zone 245 including a catalyticdistillation zone 247. The use of a catalyst in the catalyticdistillation zone 247 allows simultaneous distillation and catalyticreactions in a single contacting section or the dual functions ofdistillation and catalytic reaction in different sections of a commoncolumn.

The fractionation zone 245 and catalytic distillation zone 247 areoperated at conditions effective to further react and fractionate thecoal tar stream 230. The catalytic distillation zone 247 can operate ata wide variety of temperatures depending on the catalyst type, thepresence of hydrogen, and the location of the catalytic distillationzone. For example, the temperatures can range from about 35° C. to about320° C. The pressure can be low, for example, about 100 kPa (g) (1 bar(0) to about 300 kPa (g) (3 bar (g)).

The coal tar feed 230 is introduced to the fractionation zone 245 in thecatalytic distillation zone 247 at a point below the draw for fraction265 and above where pitch fraction 270 is removed. The catalyticdistillation zone 247 extends from the coal tar feed inlet to a positionbelow where the product draws are taken. The location for the catalyticdistillation zone will be a function of the catalyst type andproperties, and the presence or absence of hydrogen. More activecatalysts need a lower temperature to be effective and will be locatedhigher in the column. The length of the catalytic distillation zone is afunction of the space velocity needed for complete conversion, with amore active catalyst needing less volume. No particular apparatus orarrangement is needed to retain the catalyst bed within the distillationzone and a variety of methods can be used to incorporate the bed orregion of catalyst within the distillation zone. For example, catalystmay be retained between suitable packing materials or may beincorporated on to a distillation tray itself.

In one example, the catalytic distillation zone 247 contains ahydrogenation or hydrotreating catalyst, as described above. Duringfractionation, the coal tar stream 230 contacts the catalyst and atleast a portion of the organic and ionic forms of mercury react to formelemental mercury. The reactions can take place in the liquid or vaporphase.

The elemental mercury and inorganic mercury compounds are removed fromone or more streams as described above, and further treated and/orrecovered, if desired. The mercury can be recovered by vacuumdistillation at high temperature (typically about 600° C.), for example.The treaters can be operated in a lead-lag mode in series. When thefirst one is spent, flow switches to the second treater to allow forcontinuous protection.

As illustrated, the coal tar feed 230 is separated into gas fraction250, hydrocarbon fractions 255, 260, and 265 having different boilingpoint ranges, and pitch fraction 270.

One or more of the fractions 250, 255, 260, 265, 270 can be furtherprocessed, as desired. As illustrated, fraction 260 can be sent to oneor more hydrocarbon conversion zones 275, 280. Fraction 260 can be sentto hydrocarbon conversion zone 275 for hydrotreating to remove sulfurand nitrogen. Effluent 285 is then sent to hydrocarbon conversion zone280 for hydrocracking, for example, to produce product 290.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient road map for implementing an exemplary embodiment of theinvention. It being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope of the invention as setforth in the appended claims.

What is claimed is:
 1. A process for removing mercury from a coal tarproduct comprising: providing a coal tar stream; contacting the coal tarstream with a solvent in a solvent extraction zone to remove at leastone product from the coal tar stream forming at least one product streamand a remainder coal tar stream, the at least one product streamcontaining one or more of elemental mercury, organic mercury compounds,and inorganic mercury compounds; contacting the at least one productstream with an adsorbent material in an mercury removal zone, theadsorbent material comprising one or more adsorbents, an ion exchangematerial, or mixtures thereof to remove the one or more of elementalmercury, organic mercury compounds, and inorganic mercury compounds; andseparating the remainder coal tar stream into at least two fractions. 2.The process of claim 1 further comprising separating the solvent fromthe at least one product stream before contacting the at least oneproduct stream.
 3. The process of claim 1 further comprising separatingthe solvent from the at least one product stream and recycling theseparated solvent to the solvent extraction zone.
 4. The process ofclaim 1 wherein the at least one product stream contains organic mercurycompounds, and further comprising converting the organic mercurycompounds to elemental mercury before contacting the at least oneproduct stream.
 5. The process of claim I wherein the solvent comprisesa supercritical fluid, an ionic liquid, a polar solvent, andcombinations thereof.
 6. The process of claim 5 wherein solventcomprises the supercritical fluid and wherein the supercritical fluid isselected from the group consisting of supercritical NH3, supercriticalCO₂, supercritical ethane, supercritical propane, supercritical butane,supercritical water, and combinations thereof.
 7. The process of claim 5wherein the solvent comprises the ionic liquid, and wherein the ionicliquid is selected from the group consisting of imidazolium-based ionicliquid, pyrrolidinium-based ionic liquid, pyridinium-based ionic liquid,sulphonium-based ionic liquids, phosphonium-based ionic liquids,ammonium-based ionic liquids, caprolactam-based ionic liquids, andcombinations thereof.
 8. The process of claim 5 wherein the solventcomprises the polar solvent, and wherein the polar solvent is selectedfrom the group consisting of pyridine, N-methyl pyrrolidone, methylenechloride, benzyl alcohol, formamide, dimethylformamide,dimethylsulfoxide, dimethylsuccinate, dimethyladipate,dimethylglutarate, propylene carbonate, methyl soyate, ethyl lactate,tripropylene glycol (mono)methyl ether 1,3-dioxolane and combinationsthereof.
 9. The process of claim 1 wherein the adsorbent material is theone or more adsorbents and wherein the adsorbent is a noble metaldeposited on a support selected from the group consisting of molecularsieves, alumina, activated carbons, and silica gel.
 10. The process ofclaim 1 wherein the adsorbent material is the one or more adsorbents andwherein the adsorbent is a silver impregnated zeolite selected from thegroup consisting of faujasites (13X, CaX, NaY, CaY, and ZnX),chabazites, clinoptilolites and LTA (3A, 4A, 5A) zeolites.
 11. Theprocess of claim 1 wherein the adsorbent material is the one or moreadsorbents and wherein the adsorbent is sulfur or a metal sulfide on anactivated carbon support or an activated alumina support or othersupports to bind the active reagents for mercury removal in the form ofbeads or pellets.
 12. The process of claim 1 wherein the adsorbentmaterial is the one or more adsorbents and wherein the adsorbent is ametal sulfide, metal oxide, or metal carbonate on a support, the metalis selected from the group consisting of copper, silver, gold, antimony,lead, and manganese, and the support selected from the group consistingof activated alumina, clay, or activated carbon.
 13. The process ofclaim 1 wherein the adsorbent material is the one or more adsorbents andwherein the adsorbent is a metal, a metal oxide, or a metal carbonate ona support, the metal selected from the group consisting of copper,silver, gold, antimony, lead and manganese, and the support selectedfrom the group consisting of activated alumina, clay, and activatedcarbon, wherein the adsorbent is sulfided by sulfur compounds in themercury removal zone to produce a sulfided adsorbent and wherein thesulfided adsorbent removes mercury.
 14. The process of claim 1 whereinthe adsorbent material is the ion exchange material and wherein the ionexchange material contains chemically bound sulfide groups.
 15. Theprocess of claim 1 wherein the adsorbent material is the ion exchangematerial and wherein the ion exchange material comprises a cationexchange material.
 16. The process of claim 1 further comprisingprocessing at least one of the fractions to produce at least oneadditional product.
 17. A process for removing mercury from a coal tarproduct comprising: providing a coal tar stream, the coal tar streamcontaining one or more of elemental mercury, organic mercury compounds,and inorganic mercury compounds; introducing the coal tar stream into acatalytic distillation zone of a fractionation zone to separate the coaltar stream into at least two fractions, the catalytic distillation zonepositioned above a bottoms outlet and below a first product draw of thefractionation zone, the catalytic distillation zone containing acatalyst, the organic and ionic mercury compounds reacting in thepresence of the catalyst to form elemental mercury in the catalyticdistillation zone; and treating at least one of the fractions to removethe elemental mercury.
 18. The process of claim 17 further comprisingintroducing hydrogen into the catalytic distillation zone.
 19. Theprocess of claim 17 wherein the catalyst comprises at least one GroupVIB, Group VIIB, or Group VIIIB metal, a noble metal catalyst, or azeolitic catalyst.
 20. The process of claim 17 wherein the catalyticdistillation zone operates at a temperature in a range of about 35° C.to about 320° C.